This invention relates to an adjustable cement head manifold connector and subcombinations thereof. It is particularly useful in the environment in placing a cement casing in a drilled oil well. The general technique of placing a casing in a well is set forth in a brochure of the Dowell Division of Dow Chemical Company entitled "Cementing Fundamentals," the contents of which are incorporated herein by reference.
After a well is drilled, it is usually full of drilling mud. Special equipment is used to displace some of the drilling mud and pump cement down the casing and into the surrounding annulus of the well. The amount of cement used and the pressures encountered are at least partially determined by the volume and depth of the well, and often reach 10,000 pounds per square inch. The cement head, which is connected to a large pump, has a manifold leading to it. The manifold connects to at least two openings, and sometimes more, in the cement head. The cement head has the purpose of holding a wiper plug which is designed to be run inside the casing ahead of or behind the cement slurry. These plugs help prevent contamination between the cement and the drilling fluids as they move down inside the pipe. The plugs also help remove drilling mud that adheres to the inside of the casing.
The cement head provides a connection between a cement pump and the well. The cement pump pumps cement through the manifold into the head. There are usually at least two valves for diverting the pumped fluid either below the plugs in the cementing head or above them when it is desired to push them down the casing. The cementing head has a cap that can be removed for inserting the cement plugs.
During a cementing job a bottom wiper plug is placed in the cementing head and held in place by a wiper plug retainer. Drilling fluid is pumped through the bottom valve until the fluid has been circulated from the surface down the casing and up the annulus back to the surface. The wiper plug retainer valve is then opened and the cement slurry is pumped through the top valve. The cement slurry pushes the bottom wiper plug down inside the casing.
After all the slurry has been displaced, the pumping is stopped and a top wiper plug is placed in the cementing head. Then drilling fluid or water is pumped through the top valve, which forces the top wiper plug down inside the casing. Pumping is continued until the top wiper plug seats on the top of the float collar. The well is then shut in until the cement has had time to set.
Because of the harsh environment encountered during the cementing of an oil well, the manifold must be very sturdy, have a well-engineered design, and be leakproof. Moreover, because the inlet and outlets of cement heads vary somewhat in their spacings, many different manifolds have to be utilized. Because of the many different spacings of inlets, sometimes the wrong manifold is forced into place. Accordingly, leaks occur which could cause damaging results to people and equipment.
It is the desire of this invention to provide a safe manifold which can be utilized with many different cement heads in a quick, efficient, and safe manner. By utilizing a variable length of the connection between the two unions, this result has been accomplished.
Another problem with the manifolds presently used for cementing wells is that the relatively long horizontal piece from the cement head to the inlet pipe causes an excessive amount of torque, which results in cracks and breaks. Accordingly, it is highly desirable to minimize the horizontal distance from the line bringing in the cement to the cement heads. In almost all conditions, a valve has to be placed between the line and the head so that, as mentioned above, the flow can be diverted. In the past, a number of nipples and retainer rings and nuts have been utilized, but not in a satisfactory manner. Often, the manifold has had to be suspended in different ways in order to relieve some of the forces on it to prevent cracking.
One of the results of this invention has been to design a connecting means which has considerably foreshortened the horizontal distance from the cement head to the inlet line, and thus reduce the torque arm which causes damage to the manifold valve or cement head.
The result of this invention is to provide an adjustable manifold which is safer to use because of its shorter connection to the cement head and which is easily tightened in place in a fluidtight manner for many different spacings of connectors on the cement heads.